Acrylonitrile polymer composition stabilized with metal formaldehyde sulfoxylate, phosphorus pentroxide, and sulfuric acid and method of making same



United States Patent 2,878,231 ACRYLONITRILE POLYMER COMPOSITION STA- BILIZED WITH METAL FORMALDEHYDE SUL- FOXYLATE, PHOSPHORUS PENTOXIDE, AND

SULFURIC ACID AND METHOD OF MAKING SAME Charles H. Campbell and Lloyd T. Jenkins, Decatur, Ala., assignors to The Chemstrand Corporation, Decatur, Ala., a corporation of Delaware 17 Claims. (Cl. 260-326) This invention relates to the stabilization of acrylonitrile polymers and blends thereof. More particularly, it relates to the stabilization of acrylonitrile polymers and blends thereof which have a tendency to develop color upon standing or application of heat.

The term polymer, as employed in the instant description and claims, is intended to include homopolymers, copolymers, and blends thereof, said polymers containing at least 80 percent by weight of polymerized or copolymerized acrylonitrile in the polymer molecule.

Acrylonitrile polymers containing. 80 percent or more of acrylonitrile are generallyinsoluble in the more common solvents. In those instances where suitable solvents have been found, in order to effect solution, the application of heat is usually necessary. Where heat is employed to effect solutions, from which shaped articles are to be formed, a tan to dark brown color frequently develops in the solutions and therefore is carried over into the product formed therefrom. This color also develops in solutions upon standing for prolonged periods of time.

The mechanism which causes color formation has not been definitely ascertained, although .a variety of reasons therefor have been advanced. The presence of metal ions, such as iron,copper and manganese in the solutions may cause the color. The employment of amide compounds as solvents may result in formation of amines when heat is applied and cause color in the compositions. Impurities present in the solvents have also been cited as a cause.- Whatever maybe the reason for color formation, it results in compositions and products of undesirable standards and therefore, has been the source of concern, particularly in commercial operations where such types of polymers or copolymers are employed.

Accordingly, it is an object of the present invention to prevent undesirable color formation in acrylonitrile polymer compositions.

prepared in a Another object is "to minimize color formation when solutions of the acrylonitrile polymers are permittedto stand for a prolonged period-of time or upon application ofheat.

- It is also an object of'the invention to prevent color formation in acrylonitrile polymers at elevated temperatures. t

A still further object of the invention is the production of solutions of acrylonitrile polymers and articles produced therefrom having improved color characteristics.

Other objects and advantages will be apparent from a consideration of the description of the invention which follows hereafter.

In general, the objects of the invention are accomplished by dissolving the polymer of acrylonitrile in a suitable solvent therefor and preventing or minimizing color formation by the presence in the solution as an which may be employed in practising the instant invention are those having the general formula,

0 I R O-M in which R is an alkanol group containing 1 to 3 carbon atoms, an acyl group containing 1 to 3 carbon atoms or an aryl group containing 6 to 8 carbon atoms, n is an integer from 1 to 2, and M is sodium, potassium, zinc, etc. Compounds illustrative of this class are sodium formaldehyde sulfoxylate, zinc formaldehyde sulfoxylate, potassium formaldehyde sulfoxylate, zinc acetaldehyde sulfoxylate, sodium acetaldehyde sulfoxylate, potassium acetaldehyde sulfoxylate, zinc propionaldehyde sulfoxylate, sodium propionaldehyde sulfoxylate, potassium propionaldehyde sulfoxylate, and the like.

The components of the inhibiting agent may'be em ployed in equal or unequal amounts, any one constituent being present in a range of from 98 to 1 percent in a three component system. The total amount of inhibiting agent may be employed in a range of about 0.3 to 15 percent, based on the total polymer weight. However, it is preferred that the inhibiting agent of the instant invention be present in a small amount compared to the amount of polymer dissolved. Thus, although the amount is not critical, it is preferred that the inhibiting agent be present in the amount of about 0.3 to 3 per cent, based on the total weight of the polymer; The inhibiting agent may be added to the solvents before or after the polymer is dissolved therein. The inhibiting agent permits exposure to high temperatures for prolonged standing periods without the development Ofthe. objectionable color which usually results in such solutions. The compositions of the instant invention may be varying temperature range. For example, the compositions of the instant invention maybe prepared by mixing the polymer, a suitable solvent and the inhibiting agent at any temperature or heating the mixture to a temperature up to the boiling point of the solvent.

Other acids which may be employed in the practice of the present invention are nitric acid, phosphoric acid, hypophosphorous acid, hydrochloric acid, and the like.

Among thesolvents which may be used in practising mers employed in the instant invention are those containing at least percent of acrylonitrile, generally recognized as the fiber-forming acrylonitrile polymers, it will be understood that the invention is likewise applicable to polymers containing less than 80 percent acrylonitrile and the same stability is realizedwith the inhibiting agentsdefined herein. The acrylonitrile polymers containing less than 80 percent acrylonitrile; are useful in forming films, coating compositions, molding operations, lacquers, etc., in all of which applications the alleviation of undesirable color is extremely important.

For example, the polymer may be a copolymer of from 80 to 98 percent acrylonitrile and from 2 to 20 suspension polymerization wherein percent of another monomer containing the C=C linkage and copolymerizable with acrylonitrile. Suitable mono-olefinic monomers include acrylic, alpha-chloroacrylic and methacrylic acids; the acrylates, such as. mthylmethacrylate, ethylmetliacrylate, butylmethacry late, methoxymethyl methacrylate, beta-chloroethyl methacrylate, and the corresponding esters of acrylic and alpha-chloroacrylic acids; vinyl chloride, vinyl fluoride, vinyl bromide, vinylidene chloride, l-chloro-l-bromoethylene; methacrylonitrile; acrylamide and methacryl amide; alpha-chloroacrylamide, or monoalkyl substitution products thereof; methyl vinyl ketone; vinyl carboxylates, suchsas vinyl. acetate, vinyl chloroacetate, vinyl propionate, and vinyl stearate; N-vinylimides, such as N-vinylphth'alimide. and. N-vinylsuccinimide; methylene malonic esters; itaconic acid and itaconic ester; N-vinylcarbazole; vinyl. furane; al'kyl vinyl esters; vinyl sulfonic acid; ethylene alpha, 'beta-dicarboxylic acidsor their anhydrides: or derivatives, such as diethylcitraconate, diethylmesaconate, styrene, vinyl naphthalene; vinyl-substituted tertiary heterocyclic amines, such as the vinylpyridines and alltyl substituted vinylpyridines, for example, 2-vinylpyridine, 4-vinylpyridine, Z-methyl-5-vinylpyridine, etc.; 1.-vinylimidazole and alkyl-substituted l-vinylimidazoles, such as. 2-, 4-, or S-methyl-l-vinylimidazole, and other C=C containing polymerizable materials.

The polymer may be a ternary interpolymer, for example, products obtained by the interpolymerization of acrylonitrile and two or more of any of the monomers, other than acrylonitrile, enumerated above. More spe cifically, and preferably, the ternary'polymer comprises acrylonitrile, methacrylonitrile, and 2-vinylpyridiue. The ternary polymers" preferably contain from 80 to 97 percentof acrylonitrile, from 1 to percent of a vinyl-- pyridine or a l-vinylimidazole, and from 1 to 18 percent of another substance, such as methacrylonitrile or vinyl chloride.

The polymer may also be a blend of polyacrylonitrile or of. a binary interpolymer of from 80 to 99 percent acrylonitrile and from 1 to 20 percent of at least one other C=C containing substance with from 2 to 50 percent of the weight of the blend of a copolymer of from 10 to 70 percent of acrylonitrile and from to 90 percent of at least one other C=C containing polymerizable monomer. Preferably, when the polymeric material comprises a blend, it will be a blend of a copolymer of 90 to 98 percent acrylonitrile and from 2 to 10 percent of another mono-olefinic monomer, such as vinyl acetate, which is not receptive to dyestutf, with a. sufiicient. amount of a copolymer of from 10 to 70 percent of acrylonitrile and from 30 to 90 percent of a vinyl-substituted tertiary heterocyclic amine, such as vinylpyridine or l-vinylimidazole, to give a dyeable blend having an overall vinyl-substituted tertiary heterocyclic amine-content of from 2 to 10 percent, based on the weight of the blend.

The polymers, useful in the practice of the present invention, may be prepared by any conventional polyr'nerization procedure, such as mass polymerization meth: ods, solution polymerization methods, or aqueous emulsion procedures. However, the preferred practice utilizes the polymer is prepared in finely divided form for immediate use in the fiber fabrication operations. The preferred suspension polymerization may utilize batch procedures, wherein monomers are charged with an aqueous medium containing the necessary catalyst and dispersing agents. A more desirable method involves the semi-continuous procedure in which the polymerization reactor containing the aqueous medium is charged with the desired monomers and the continuous withdrawal of polymer may also be employed. 7

The polymerization is catalyzed by means of any watersoluble peroxy compound, for example the potassium,

ammonium andother water-soluble salts of peroxy acids,

sodium peroxide, hydrogen peroxide, sodium perborate, the sodium salts of other peroxy acids, and any other water-soluble compound containing a peroxy group (OO). A wide variation in the quantity of peroxy compound is possible. For example, from 0.1 to 3.0 percent by weight of the polymerizable monomer may be used. The catalyst may be charged at the outset of the reaction, or it may be: added continuously or ininelements" throughout the reaction for the purpose of maintaining a more uniform concentration of catalyst in the reaction mass. The latter method is preferred because it tends to makethe resultant polymer more uniform in its chemical and physical properties.

Although the uniform distribution of the reactants throughout the reactionmasscan be-achieved by vigorous agitation, it is generally desirable, to promote the uniform distribution of reagents by using inert wetting agents, or emulsion stabilizers. Suitable reagents for'this' purpose are the water-soluble salts of fatty acids, such as sodium. oleate and potassium stearate, mixtures of water soluble fatty acid salts, such as common soaps prepared by the saponification of animal and'vegetable oils,'the amino soaps, such as salts of'triethanolamine and dodecylmethylamine, salts of rosin acids and mixtures thereof, the water-soluble salts of half esters of sulfuric acid and long chain aliphatic alcohols, sulfonated hydrocarbons, such as alkyl aryl sulfonates, and any other of a wide variety of wetting agents, which are in general organic compounds containing both hydrophobic and hydrophilic radicals. The quantity of emulsifying agents will depend upon the particular agents selected, theratio of monomer to be used, and the conditions of polymerization. in general, however, from 0.01 to 1.0 percent by Weight of the monomers maybe employed.

The emulsion polymerizations are preferably conducted in glass or glass-lined vessels which are provided: with. a means for agitating the contents. Generally, rotary stirring devices are the most elfective means of insuring, the intimate contact of the reagents, but other methods may be successfully employed, for example, by rocking or tumbling the reactors. The polymerization equipment generally used is conventional in the art' and the adaptation of a particular type of apparatus to the reaction contemplated is within the province of one skilledin the art. The articles manufactured therefrom may be pro duced by well-known conventional methods, for example, the wet-spinning, dry-spinning and melt-spinning methods for producing fibers. r

The following examples are illustrative rather than limitative and all parts, proportions and percentages are by weight unless otherwise specified.

1 EXAMPLE I.

7.5 grams of a polymer blend of 88 percent of a copolymer containing, 94 percent: of acrylonitrile and 6 percent of vinylacetate. and. 12 percent of a copolymer of 50 percent of acrylonitrile and. 5.0: percent of 'Z-methyI- 5-vinyl pyridine were added to 45 milliliters of N,N- dimethylacetarnide containing approximately 0.05 gram of titanium dioxide. The. mixture was stirred and heated to 70 C. It was then quickly cooled to room temperature and the color measured. This sample was used as a control. The purity is. set forth below. Subsequently, a like sample color inhibitor containing 0.075 gram each of phosphorous pentoxide, zinc formaldehyde: sulfoxylate and sulfuric acid. The purity is set forth below.

Table I Inhibitor Percentage Purity Used Control 11.6 Phosphorous Pentoxide, Zinc Formaldehyde Sulfoxylate and Sulfure Acid 3 4. 5

was prepared. but with 0.225 gram of a 7.5 grams of acopolyrnercontaining 94 percent of acrylonitrile and 6 percent of vinyl acetatewere added to 45 milliliters of N,N-dimethylacetamide containingap -f proximately 0.05 gram of titanium dioxide. The 'mix-- ture was stirred and heated for 35 minutes at 70 C. "It' was then quickly cooled to room temperature and the color measured. This sample was used as a control. The purity is set forth below. ;Subsjequently, a like sample was prepared but with 0.225, gram of an inhibiting agent containing 0.075 grain eachof phosphorus pentoxide,. zinc formaldehyde sulfoxylate and sulfuric acid. The purity is set forth below.', 1 f i Table II Inhibitor Percentage Purity Used t Control l0. 2 Phosphorous Pentcxide, Zinc Formaldehyde Sulfoxylate and Sulfuric Acid 3 r 4.0

EXAMPLE III 7.5 grams of an acrylonitrile homopolymer'wer added to 45 milliliters ofN,N-dimethylacetamide-' containing."

Table III Inhibitor Percentage Purity Used comm .Q. 10.8 Phosphorous Pentoxlde, Zinc Formal hyde Sulfoxylate and Sulfuric Acid Y .3 p 3. 0

The tests for color indicative of approaching whiteness used throughout the examples consist of measurements-of purity as calculated from thetristimulus values determined on" a 'GeneralElect-ric spectmphatemeter by the methods recommended by therStandard Observer and Coordinate System of the International Commissiom-on Illumination, as fully set forth in the Handbook ofColorimetry published by The Technology Press, Massachusetts Institute of Technology" in 1936- 1 The compositions of the instant invention present many advantages? "For' 'ex'ampre prbauets' formed from the polymer solutions of the instant invention are free of objectionable color and therefore of greater commercial value. In preparing the polymer solutions, heat may be applied without the danger of color formation and the solutions, if necessary, may stand for prolonged periods and remain free of color. The inhibiting agents are readily available and inexpensive. Therefore, no great increase in production cost is necessary. The compositions containing the inhibitors may be prepared without going through detailed and elaborate procedures that necessitate expensive changes in the design of the apparatus used to manufacture them.

It will be understood to those skilled in the art that many apparently widely difierent embodiments of this invention can be made without departing from the spirit and scope thereof. Accordingly, it is to be understood that this invention is not to be limited to the specific em bodiments thereof except as defined in the appended claims.

l. A new composition of matter comprising a poly mer containing at least 80,percent of polymerized acrylonitrile and up to 20 percent of another polymerizable mono-olefinic monomer copolymerizable therewith, a solvent therefor, and an inhibiting Qagent containing substantially equal proportions by weight of a compound having the general formula,

wherein R is an alkanol group containing 1 to 3 carbon atoms and having the free valence on a carbon atom joined to the hydroxy group, n is an integer from 1 to 2, and M is a metal selected from the group consistingof sodium, potassium and zinc; phosphorous pentoxide and sulfuric acid. a

2.A new composition of matter as defined in claim 1 wherein the polymer is a copolymer containing from to 98 percent of acrylonitrile and from 2 to 20 percent of another polymerizable mono-olefinic monomer copolymerizable therewith. t

3. A new composition of matter as defined in claim 1 wherein the polymer is a blend of 80 to 99 percent of (A) a copolymer containing to 98 percent of acrylonitrile and 2 to 10 percent of vinyl acetate and 1 to 20 percent of (B) a copolymer containing 10 to'i0 percent. of acrylonitrile and 30 :to. 90 percent of Z-methyl-S-vinylr pyridine. l

4. A new composition of matter as defined' in claim -l wherein the polymer is polyacrylonitrile.

r 5. A new composition of matter as defined in claim wherein the compound is sodium formaldehyde sulfoxylate.

6. A new composition of matter as defined in claim 1 wherein the compound is potassium formaldehyde sulfoxylate.

7. A new composition of matter as defined in-claim 1 wherein the compound is zinc formaldehyde sulfoxylate.

8. A new composition of-matteras defined in claim 1 wherein the solvent is N,N-dimethylacetamide.

9. A new composition of matter comprising a polymer blend of (A) a copolymer containing 90 to 98 percent of acrylonitrile and 2 to 10 percent of another polymerizable mono-olefinic monomer and (B) a copolymer containing 10 to 70 percent ofacrylonitrile and 30 to 90-percent of a vinyl-substituted tertiary heterocyclic amine, said blend having an overall vinyl-substituted tertiary heterocyclic amine content of from 2 to 10 percent based on We h t -:b s drel sol en -th efor. a d a wherein R is an alkanol group containing 1 to 3 carbon atoms and having the free valence on a carbon atom joined to the hydroxy group, n is an integer from 1 to 2, and M is a metal selected from the group consisting of sodium, potassium and zinc; phosphorous pentoxide and sulfuric acid.

10. A new composition of matter comprising a copolymer containing 80 to 98 percent of acrylonitrile and 2 to 20 percent of vinyl acetate, a solvent therefor, and 0.3 to 15 percent, based on the total weight of the polymer, of an inhibiting agent, said inhibiting agent containing substantially equal proportions by weight of a compound having: the general formula,

wherein R is an alkanol group containing 1 to. 3v carbon atoms and having the free valence on a carbon atom joined to the hydroxy group, n is an integer from 1 to 2, and Mis a metal selected from the group consisting of sodium, potassium and zinc; phosphorous pentoxide and sulfuric acid.

11. A new composition of matter comprising a polymer blend of 80 to 99 percent of (A) a copolymer containing 90. to: 98 percent. of. acrylonitrile and 2. to. percentof, vinyl acetate and 1v to 20. percent of (B) a copolymer containing. l0v tov 70 percent of acrylonitrileand 3.0 to, 90. percent of 2-methyl-S-vinylpyridine;. a solvent therefor,

and 0.3 to percent, based on the total weight of. the

polymer, of an inhibiting agent, said inhibiting agent. containing; substantially equalproportions, by weight of a compound. having the general formula,

sodium, potassium and zinc; phosphorous pentoxide and sulfuric. acid.

12. A new composition of matter comprising a polymercontaining at: least 80 percent of polymerized acrylonitril'e and up: to. 20. percent of another polymerizable mono-olefinic monomer copolymerizable therewith, a solvent therefor, and 03 to. 15. percent, based on the total weight, of the polymer, of an inhibiting agent, said inhibiting agent containing substantially equal proportions.

by weight. of. acompound having the general formula,

0 Sf n o M wherein R is an alkanol group containing 1 to 3 carbon atoms and having the free valence on a carbon atom joined to'the'hydroxy group, n is an integer from, 1 to 2, and M is a metal selected from the group consisting of sodium, potassium and zinc; phosphorous pentoxide and sulfuric acid.

13'. A method for preparing anew composition of J7 wherein R is an alkanol' group containing 1 t0 3. carbon atoms and having the free valence on a carbon atom joined to the hydroxy group, n. is an integer from 1 to 2,

and M. is. a. metal. selected from. the groupv consisting of. sodium, potassium, and zinc; phosphorous. pentoxide and sulfuric acid, and heating the mixture to form a homogeneous; solution.

14. The method as, defined in claim 13 wherein the,

polymer isa copolymer'containingjrom to 9.8 percent of acrylonitrile and from 2 to 20 percent of another polymerizable mono-olefinic monomer. copolymerizable there with.

15*. The method as defined in. claim 13 wherein the polymer a, blend of: 80. to- 9.9- percent of (A)v a copoly-- men containing to 98: percentof acrylonitrile. and 2 to 10 percent; of vinyl, acetate and 1 to 20 percent of (B:). a copolymer containing 10 to 70. percent of acrylonitrile 30 to:9.0;- percentof Z-methyl S-vinyl pyridine.

16. 'Ihemothod; as defined in claim: 13; wherein the'polymer: lSf polya'erylonitrile.

17 .v A method for preparing a new composition of matten comprising. mixing a. polymer blend of 80. to 99 percent of- (A) a copolymer containing 9.0 to 98.percent of acrylonitrile and 2 to 10 percent of vinyl acetate and l to 20 percent of (B) a copolymer containing 10 to 70 percent ofi acrylonitrileand" 30 to 90'percent of Z-methyl- S-vinyl pyridine; a solvent therefor, and 0.3 to 15 percent, based on the total weight of the polymer, of an inhibiting agent, said inhibiting agent containing substantially equal. proportions by weight of zinc formaldehyde sulfoxylate, phosphorous pentoxide and sulfuric acid"; and heating the mixture to a temperature in a range of 25"" C; to the" boiling point of said. mixture to form a homogeneous solution.

References Cited in the file of this: patent UNITED STATES PATENTS 2 ,502,030 Scheiderbauer Mar. 28', 1950 2,642,408 Stanin et a1. June 16,. 1953 FOREIGN PATENTS 1,027;4i,4;$ Fiancev May 12,, 195.3 

1. A NEW COMPOSITION OF MATTER COMPRISING A POLYMER CONTAINING AT LEAST 80 PERCENT OF POLYMERIZED ACRYLONITRILE AND UP TO 20 PERCENT OF ANOTHER POLYMERIZABLE MONO-OLEFINIC MONOMER COPOLYMERIZABLE THEREWITH, A SOLVENT THEREFOR, AND AN INHIBITING AGENT CONTAINING SUBSTANTIALLY EQUAL PROPORTIONS BY WEIGHT OF A COMPOUND HAVING THE GENERAL FORMULA 